1. Technical Field
The invention relates to isolated nucleic acids that can be used to direct expression of a second nucleic acid operably linked thereto.
2. Background Information
Recombinant DNA technology has provided a new opportunity for engineering valuable traits in plants. Basically, foreign genes can be introduced into plants to alter metabolic pathways. Examples of products of plant metabolic engineering include herbicide tolerant plants, long-life tomatoes, improvement of seed nutritional quality, and production of novel compounds of industrial or pharmaceutical value. In some cases, engineering of new traits was made possible by the expression or suppression of a single gene while in other cases the expression or suppression of multiple genes during seed development was required.
Plant promoters that have been characterized to date include constitutive promoters such as promoters of actin and ubiquitin genes; promoters of genes involved in photosynthesis, such as the small subunit of ribulose 1,5-bisphosphate carboxylase and the chlorophyll a/b binding protein; root specific promoters identified upstream of mannopine synthase, putrescine N-methyltransferase, and hyoscyamine 6b-hydroxylase genes; promoters of patatin and sucrose synthase genes which direct specific expression in potato tuber; seed specific promoters of genes encoding lipoxygenase and lectin, oilseed rape napin, cruciferin, and oleosin, bean phaseolin and arcelin-5, oleate 12-hycroxyalse, rice amylase and glutelin, maize zein, and wheat puroindoline. Inducible promoters such as promoters of pathogenesis-related protein genes, promoters of heat shock proteins and herbicide inducible promoters of glutathione S-transferase. Artificial promoters like the regulation of maize CAB promoter with E. coli lac repressor/operator system; the Tet repressor system; the induction system using animal steroid hormone receptors; copper controlled system using promoter elements of metallothionein gene; and fungal promoters induced by ethanol.
Seed storage proteins accumulate in discrete vesicles of protein bodies and constitute a major fraction of the proteins found in the mature seed. Seed storage proteins are used as sources of amino acids during germination and post-germinative growth of seedlings. Their corresponding mRNAs accumulate to high levels during the maturation phase and are mainly under transcriptional regulation. Seed storage proteins can be classified on the basis of their solubilities in various extraction solvents. The albumins are water-soluble, globulins are salt-soluble, prolamins are alcohol/water-soluble and glutelins are acid or alkali soluble. The globulins are further subdivided, based on their sedimentation coefficients, into two types, the 7S vicilin-type and the 11S legumin-type globulins.
Sesame (Sesamum inidicum L.) has been an important oil crop in Asian countries. Sesame seed contains approximately 50% oil and 19% protein. Approximately 70-85% of the oil is oleic and linoleic acids, which makes sesame a good source of edible oil. Sesame seed contains high levels of methionine, partly due to a sulfur-rich 2S albumin isoform, which contributes to its nutritional quality. Because of its flavor and nutrient content, sesame is directly consumed as an additive in food. The two major storage proteins in sesame are 11S globulin and 2S albumin, which constitute 80-90% of total seed protein. Recently, full-length cDNAs encoding 2S albumin, 11S globulin, and 7S globulin isoforms have been reported.